Domains and outcome measures for the assessment of limited cutaneous systemic sclerosis: an international collaborative scoping review

Objectives:
The aim of this study was to comprehensively identify instruments within relevant domains employed to assess lcSSc since the endorsement of its consensus definition in 1988. The overall objective is to inform the creation of a Combined Response Index for Scleroderma Trials Assessing lcSSc (CRISTAL).

Methods:
MEDLINE and Embase were searched using terms selected to comprehensively retrieve titles and abstracts mentioning both lcSSc and dcSSc, along with those only mentioning lcSSc, SSc sine scleroderma, limited SSc and/or CREST/CRST. Because our initial assessment of the literature revealed that very few studies included only lcSSc subjects, we also assessed literature that included both cutaneous subsets. A total of 3964 titles and abstracts were screened by two reviewers, and 270 articles were selected for data extraction.

Results:
We identified 27 domains encompassing 459 instruments. Instruments from ‘Skin involvement’, ‘Pulmonary involvement’ and ‘Health-related quality of life and general functioning’ were the most frequently retrieved. Among the 15 most represented instruments announced as primary end points in efficacy or effectiveness studies, 7 were clinician-reported outcomes (ROs), 7 were patient ROs, and one was a performance outcome (6 min-walk test). The mean proportion of lcSSc patients in studies of lcSSc, including studies that mention both lcSSc and dcSSc, was 56.4%, demonstrating that this subset is underrepresented in the literature, given that the prevalence of lcSSc ranges from 60% to 80% in national registries and international cohorts.

Conclusion:
This scoping literature review provides a comprehensive identification of domains and outcomes used to assess lcSSc. Our results also highlight that lcSSc is underrepresented in the literature.